1. Field of the Invention
The invention relates to lightweight concrete masonry units.
2. Description of the Related Art
Concrete masonry units are specified as width by height by length (w.times.h.times.1). The overall dimensions of concrete masonry units are accurate to plus or minus one-eighth inch. These dimensions vary with different manufacturers and project requirements and there are a variety of configurations of concrete masonry units. A typical masonry unit has a nominal face size of 8" high.times.16" long (75/8".times.155/8" actual).times.thickness indicated.
Units may be manufactured with two or three cores, straight ends (typical of corners), or with ears or flanges. Unit configurations vary with local preferences for placing units; manufacturing equipment and processes; concrete mixes; and product performance requirements.
Split-face concrete masonry units provide an appearance of natural stone. The units are typically manufactured as two units connected together as one. Equipment splits or fractures the one unit into two separate blocks and the "face" or visible side of the unit then has a unique texture created by the random breakage of the face area and by fracturing of aggregates in the unit mix.
The units are typically available in a variety of colors, sizes, and configurations. Additionally, units may be scored, ribbed or fluted for additional accents patterns.
Architectural concrete masonry also includes smooth-face or "matte face" units. These units are not split as described above and therefore have a smooth, flat appearance. These are also produced in a variety of configurations, sizes, and colors.
The standards for lightweight aggregates for concrete masonry units are set forth in ASTM C331. There are three general types of lightweight aggregates, as follows:
(1) aggregates prepared by expanding, pelletizing, or sintering products such as blast-furnace slag, clay, diatomite, fly ash, shale, or slate; PA1 (2) aggregates prepared by processing natural materials, such as pumice, scoria, or tuff; and PA1 (3) aggregates consisting of end products of coal or coke combustion. PA1 (1) cement--about 11 to 11.5% by weight; PA1 (2) pumice lightweight aggregate--about 47 to 47.5% by weight; PA1 (3) other aggregate--about 22.5 to 23% by weight; PA1 (4) sand--about 18 to 18.5% by weight; PA1 (5) liquid color pigment--as required to provide a desired color, typically 14 to 17 pounds; and PA1 (6) liquid admixture(s)--as required to meet water impermeation standards. PA1 (1) Approximately 25% reduction in the actual weight of the unit. Current colored masonry units typically weigh 40-60 pounds. The new masonry units are in the 30-45 pound range; PA1 (2) Less load weight in building design; PA1 (3) The same strength as other heavier units. The new masonry units meet all ASTM C90 compressive strength requirements; PA1 (4) Improved insulating value. According to the National Concrete Masonry Association TEK Report 6-1A, Table 1, the pumice aggregate raises the standard R-value of the unit; PA1 (5) Improved fire resistance rating. The pumice gives the finished unit a higher fire resistance rating, according to National Concrete Masonry TEK Report 7-1, Table 6.0; and PA1 (6) Inherent design makes the units less susceptible to water permeation compared to other lightweight units. The units not only achieve the lighter weight, but also achieve a higher water impermeation standard. The mix design and ingredients of the units inhibit water from wicking through the block's faceshell and reaching the interior of the wall. Unlike other lightweight units that inhibit water permeation through application of surface-applied sealants, the present units achieve this by their inherent characteristics. Surface sealants are subject to improper application and natural deterioration over time; therefore, the inherent water impermeation qualities of the present units make them a unique lightweight unit.
The aggregates are composed predominately of lightweight-cellular and granular inorganic material.
The standards for loadbearing concrete masonry units are set forth in ASTM C90. The standards relate to hollow and solid concrete masonry units made from portland cement, water, and mineral aggregates with or without the inclusion of other materials. There are three classes of concrete masonry units including lightweight. There are two types of concrete masonry units: (1) Type I, moisture-controlled; and (2) Type II, nonmoisture-controlled. These units are suitable for both load-bearing and nonloadbearing applications. The moisture content requirements for Type I units are shown in Table 1 of ASTM C90.
Although standard gray lightweight masonry units have been manufactured for many years, there has been a need in the art for a lightweight colored masonry unit. Many lightweight units are expanded shale and slag, but due to the dark gray color of these materials, they are not suitable for production of light-colored masonry units.
An object of the present invention is to provide a lightweight concrete masonry unit with the material weight classification less than 105 pounds per cubic foot.
A further object of the present invention is to provide a lightweight concrete masonry unit which meets all ASTM C90 specifications and achieves stringent water impermeation requirements.
A still further object of the present invention is to provide a lightweight concrete masonry unit which is designed so that a manufacturer can manufacture them in a repetitive manner.
Yet a further object of the present invention is to provide a lightweight, light-colored masonry unit.